JP2000318193A - Image recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the overheating of a printing head even in such a case that the ratio of black data among printing data is high in an image recording apparatus. SOLUTION: The temp. rise value (B) of a printing head estimated on the basis of the ratio of black data among printing data calculated with respect to a next printing block is added to the present detection temp. (A) of the printing head (#4) to calculate the estimate temp. (A+B) of the printing head at the time of next block printing and, when this estimate temp. exceeds an overheating limit value (#5; YES), a predetermined standby time is set at every scanning corresponding to the predetermined line of the printing head (#7) and the thermal printing of the printing head is allowed to stand by at every printing corresponding to the predetermined line. By this constitution, the overheating of the printing head can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus such as a facsimile apparatus and a printer, and more particularly to a technique for preventing a print head from overheating.

[0002]

2. Description of the Related Art In a conventional image recording apparatus, a printing speed is controlled on the basis of an amount of print data received from a communication device of a communication partner in a memory, thereby smoothly changing a printing speed for each line. To prevent the occurrence of printing unevenness (see, for example, Japanese Patent Laid-Open No. 7-212).
No. 550). Also, in a conventional thermal printing type image recording apparatus, if there is a waiting time until the next line of print data is received, the print time of the last line of print data in the already received print data is extended. In some cases, the occurrence of a print blank area is prevented (see, for example, JP-A-3-208462).

[0003]

However, the conventional image recording apparatus for controlling the printing speed from the viewpoint of preventing the occurrence of the printing unevenness as described above, and the printing data of the printing data from the viewpoint of preventing the occurrence of the blank printing area. In the image recording apparatus that controls the printing time, the printing speed and the printing time are not controlled in consideration of the temperature of the printing head. Therefore, the printing head is a thermal type, and the black data (printing data) in the printing data is used. If the ratio of the data corresponding to the dots to be printed in) is high, the print head may overheat.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has been made to prevent the print head from overheating even when the ratio of black data in the print data is large. It is an object of the present invention to provide an image recording apparatus capable of reducing occurrence of an unusable state of the apparatus.

[0005]

According to the present invention, there is provided an image recording apparatus for scanning a print head to record an image on a recording medium, comprising: storage means for storing print data; A print head for heating and printing the print data on the recording medium based on the print data stored in the printer, a head driving means for driving and scanning the print head along the recording medium, and printing for determining the ratio of black data in the print data The apparatus includes data analysis means and control means for controlling timing of driving scanning of the print head by the head driving means in accordance with the ratio of black data in the print data obtained by the print data analysis means.

In the above arrangement, the ratio of black data in the print data is obtained by the print data analyzing means, and the timing of the driving scan of the print head by the head driving means is controlled in accordance with the ratio of the black data. Accordingly, the timing of the heating print of the print head, which is determined according to the timing of the drive scan of the print head, is controlled according to the ratio of the black data in the print data. Even in the case of a large number, the print head does not overheat.

The printing apparatus further comprises a detecting means for detecting the temperature of the print head, wherein the control means sets the print temperature obtained by the print data analyzing means for the block to be printed next to the current temperature of the print head detected by the detecting means. When the temperature obtained by adding the expected temperature rise of the print head based on the ratio of black data in the data exceeds the overheat limit value of the print head, a predetermined value is set for each scan of the print head for a predetermined line by the head driving unit. It is desirable to set a waiting time for the user. Thus, when the expected temperature of the print head when the next block to be printed is printed exceeds the overheat limit value of the print head, the heating print of the print head performed in synchronization with the drive scan of the print head for a predetermined number of lines is performed. Since it is possible to make the print head stand by every time printing is performed, overheating of the print head can be prevented.

It is desirable that the predetermined standby time is set in a plurality of stages according to the degree to which the expected temperature of the print head exceeds the overheat limit value. This makes it possible to control the print head so as not to overheat without lowering the printing speed as much as possible.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image recording apparatus according to an embodiment of the present invention will be described with reference to the drawings. The facsimile apparatus according to the present embodiment is a thermal printing type image recording apparatus that records a print image on thermal paper based on print data or the like received from a communication terminal of the other party.

FIG. 1 shows a schematic configuration of an electric system of the facsimile apparatus according to the present embodiment. The facsimile apparatus 1 includes a CPU 2 for controlling the overall operation, an NCU (NETWORK CONTROL UNIT) 3 for controlling connection with a communication device of the other party, a modem 4 for converting an analog signal into a digital signal, and a storage of transmission / reception data. And a printing unit 6 for printing received data and the like stored in the buffer memory 5 and a reading unit 7 which is a scanner for optically reading a transmission original or the like. CPU2
It also functions as a print data analysis unit and a control unit described in the claims. The printing unit 6 includes a thermal head (printing head) 8 for heating and printing the thermal paper, a printing pulse generating circuit 9 for generating a printing pulse for the thermal head 8, and a printing motor (head driving unit) for driving the thermal head 8.
10, a print motor drive circuit 11 for controlling the drive of the print motor 10, a platen motor 12 for driving a platen roller for transporting the recording paper, a platen motor drive circuit 13 for controlling the drive of the platen motor 12, and a temperature of the thermal head 8. It comprises a thermistor temperature sensor 14 (detection means) for detection.

The operation of the facsimile apparatus 1 having the above configuration will be described. Data transmitted from the destination communication device via the telephone line 20 is received by the NCU 3, converted into digital data by the modem 4, and then sent to the CPU 2. The CPU 2 decomposes the received data line by line and accumulates it in the buffer memory 5 as print data.
When print data is stored in the buffer memory 5, the CPU 2 stores the print data in the buffer memory 5 as one.
Lines are sequentially taken out and transferred to a print pulse generating circuit 9 to heat the thermal head 8 according to the print data and to transmit a motor drive signal to a print motor drive circuit 11 and a platen motor drive circuit 13, The thermal head 8 and a platen roller (not shown) are driven in synchronization with the heating and printing by the thermal head 8. In this way, printing of the received data is performed. When transmitting the data read by the reading unit 7, the CPU 2
After storing the data transferred from the buffer memory 5 as transmission data in the buffer memory 5, the data is transferred to the modem 4. The data transferred to the modem 4 is converted into analog data and then transmitted from the NCU 3 to the communication device of the other party via the telephone line 20.

Next, a CPU for preventing overheating of the thermal head 8 in the facsimile machine 1 is described.
2 will be described with reference to the flowchart of FIG. If there is print data in the buffer memory 5 (YES in # 1), the CPU 2 detects the current temperature (A) of the thermal head 8 with the thermistor temperature sensor 14 (# 2) and prints stored in the buffer memory 5 (# 2). Block to be printed next in data (for example, for 10 lines)
Is read, and the ratio of black data (data corresponding to dots to be printed) in this block is calculated (#
3) The expected temperature rise value (B) of the thermal head 8 during the next block printing is calculated based on the ratio of the black data (# 4). The calculation of the expected temperature rise value (B) is performed using a table showing the relationship between the ratio of the black data in the block and the temperature rise value of the thermal head 8. The printing speed is, for example, 200 dots / second. Even if the ratio of the black data in the block is the same, since the temperature rise value of the thermal head 8 differs depending on the use environment, a test chart is printed every time the power is turned on, and the relationship between the ratio of the black data in the block and the temperature rise value. Is rewritten. Thus, the expected temperature rise value (B) of the thermal head 8 can be accurately calculated regardless of the use environment.

Next, the CPU 2 calculates the expected temperature rise value (B) of the thermal head 8 at the time of the next block printing obtained in # 4 by the current temperature (A) of the thermal head 8 detected in # 2.
Is added to obtain the expected temperature (A + B) of the thermal head 8 at the time of the next block printing, and the estimated temperature exceeds the overheat limit value of the thermal head 8 (corresponding to a threshold value for preventing an overheat error). in case of(#
(YES at 5) The calculation (# 7) and the setting of the wait time (standby time) of the print motor 9 for each one-line printing are performed, and then the print processing (# 9) is performed. Thus, the driving and heating of the thermal head 8 can be performed intermittently, so that the temperature of the thermal head 8 can be prevented from rising, and the occurrence of overheating can be prevented. However, the difference between the expected temperature (A + B) of the thermal head 8 at the time of the next block printing and the overheat limit value is the error limit value (in the case of Table 1 below, 40 ° C. in hexadecimal). If it exceeds (YES in # 6), it is determined that the thermal head 8 is already overheated, an overheat error process is performed (# 8), and the printing process is terminated.

The calculation of the # 7 wait time will be described with reference to Table 1 below. X in the table indicates the value obtained by subtracting the overheat limit value from the expected temperature (A + B) of the thermal head 8 at the time of the next block printing, indicated by hexadecimal. As shown in Table 1, the setting of the wait time is performed stepwise according to the degree to which the expected temperature (A + B) exceeds the overheat limit value.

[0015]

[Table 1]

Here, the thermistor temperature sensor 14 for detecting the temperature of the thermal head 8 will be described. As shown in FIG. 3, the thermistor is a resistor whose resistance value changes greatly with temperature, and the resistance value decreases as the temperature of the measurement target increases. The CPU 2 can detect the temperature by detecting the resistance value of the thermistor of the thermistor temperature sensor 14 and converting the resistance value to the temperature based on the temperature characteristic known in advance.

According to the facsimile apparatus 1 of the embodiment, the temperature rise value of the thermal head 8 obtained based on the ratio of the black data in the next block is added to the current detected temperature of the thermal head 8. Then, the temperature of the thermal head 8 at the time of the next block printing is predicted, and when the predicted temperature of the thermal head 8 exceeds the overheat limit value, the wait time of the print motor 9 for each line printing is set stepwise. Accordingly, the heating printing of the thermal head 8 is made to stand by for each line printing, thereby preventing the temperature of the thermal head 8 from rising. This makes it possible to prevent overheating of the thermal head 8 while keeping the printing speed of one line as high as possible without changing the printing speed itself. Therefore, the occurrence of an unusable state of the apparatus can be reduced. . In the above embodiment, the temperature of the thermal head 8 at the time of the next block printing is estimated in consideration of the current detected temperature of the thermal head 8, so that the influence of the use environment of the apparatus can be eliminated. it can.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, the temperature of the thermal head 8 may be estimated based on only the ratio of the black data in the next block, and the wait time of the print motor 9 may be set based on the estimation. Further, the current temperature of the thermal head 8 may be calculated based on the ratio of the black data in the already printed block without using the thermistor temperature sensor 14. Further, the resistance value of the thermal head 8 itself may be detected without using the thermistor temperature sensor 14. Further, the print head includes various types of heads that generate heat by driving, in addition to the thermal head 8.

[0019]

As described above, according to the present invention, the drive scan timing of the print head is controlled in accordance with the ratio of black data in the print data. The timing of the heating print of the print head determined accordingly is controlled in accordance with the ratio of the black data in the print data. Overheating can be prevented, and occurrence of an unusable state of the apparatus can be reduced.

The temperature of the print head at the time of the next block printing is predicted, and when the predicted temperature exceeds the overheat limit value of the print head, a predetermined standby time is set for each scan of the print head for a predetermined line. Accordingly, the temperature of the print head can be adjusted, and overheating of the print head can be prevented.

Further, by setting the predetermined standby time in a plurality of stages according to the degree to which the expected temperature of the print head exceeds the overheat limit value, it is possible to accurately control the print head so as not to overheat.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an electric system of an image recording apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart of a printing process of the image recording apparatus.

FIG. 3 is a diagram showing a temperature characteristic of a resistance value of a thermistor temperature sensor used in the apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Facsimile apparatus (image recording apparatus) 2 CPU (print data analysis means, control means) 5 Buffer memory (storage means) 8 Thermal head (print head) 10 Print motor (head drive means) 14 Thermistor temperature sensor (detection means)

Claims (3)

[Claims] 1. An image recording apparatus for recording an image on a recording medium by scanning a print head, comprising: storage means for storing print data; and recording the print data based on the print data stored in the storage means. A print head for heating and printing on a medium, a head driving unit for driving and scanning the print head along a recording medium, a print data analysis unit for obtaining a ratio of black data in print data, and a print data analysis unit for obtaining a ratio of black data in print data. An image recording apparatus comprising: control means for controlling a timing of driving scanning of the print head by the head driving means in accordance with a ratio of black data in the print data. 2. The print data analyzing unit according to claim 2, further comprising a detecting unit configured to detect a temperature of the print head, wherein the control unit sets the current print head temperature detected by the detecting unit to a block to be printed next. When the temperature obtained by adding the temperature rise value of the print head expected based on the ratio of the black data in the print data obtained by the above exceeds the overheat limit value of the print head, a predetermined line of the print head by the head driving means is used. 2. The image recording apparatus according to claim 1, wherein a predetermined standby time is set for each scan. 3. The image recording apparatus according to claim 2, wherein the predetermined standby time is set in a plurality of stages in accordance with a degree in which an expected temperature of the print head exceeds an overheat limit value.